Microscope used by Charles Valentine Riley (1845-1895), a British-born entomologist who settled in the United States, worked for the Smithsonian Institution, and convinced Congress to create the United States Entomological Commission. It is a compound monocular with coarse and fine focus, triple nosepiece, inclination joint, circular stage, and sub-stage iris diaphragm; the sub-stage mirror is missing. The inscription on the tri-leg base reads “Queen & Co. Philada” and “1392.”
This appears to be an Acme No. 3. Sidle & Poalk began making Acme microscopes in 1879. By 1880, the firm had moved from Philadelphia to Lancaster, and was trading as John W. Sidle & Co. and/or the Acme Optical Works. Queen & Co. took over production soon thereafter.
Describing the Queen business in April 1888, a reporter for Scientific American noted that “The microscopes of the various ‘Acme’ patterns are made here, these being finished up in lots of from 25 to 50 of a kind; many of the parts are made up by hundreds at a time. As the best drawn steel pinions to be found in the market have proved to be of insufficient exactness to make a perfect rack and pinion movement, all the pinions and racks used here in the manufacture of microscopes are cut by fine machinery specially adapted to this work. To secure smoothness in motion, each rack and pinion is ‘ground in.’ The making and adjustment of the rack and pinion is one of the most vital points of a microscope; indeed, it is an art of itself.”
Ref: James W. Queen & Co., Priced and Illustrated Catalogue of Microscopes and Accessories (Philadelphia, 1890), pp. 46-48.